1. Field of the Invention
The present invention relates to a vehicle alternator and to a method of manufacture therefor, and in particular to a construction for securing resin fans to polar cores.
2. Description of the Related Art
The vehicle alternator disclosed in Japanese Patent Laid-Open No. (HEI) 5-30707, shown in FIG. 12, is a known example of a conventional vehicle alternator.
In the center of FIG. 12, there are disposed: polar cores 5, 6 of opposite polarity, whose polar tooth portions project alternately in the axial direction around a circumference; a magnetizing coil 7 held between the polar cores 5, 6; a revolving shaft 8 to which the polar cores 5, 6 are secured; and a rotor 4 having a pair of slip rings 9, which are secured to the revolving shaft by means of an insulated sleeve. A stator 1 comprising a stator core 2 and a stator coil 3 is disposed outside the rotor 4.
A front bracket 12 and a rear bracket 13 are disposed outside the stator 1, and the front bracket 12, the rear bracket 13, and the stator core 2 are secured by fastening bolts 14. Air intake openings 12a and air discharge openings 12b are disposed in the front bracket 12 for ventilation, and air intake openings 13a and air discharge openings 13b are disposed in the front bracket 13 also for ventilation, and ventilation occurs in each as shown by the arrows in the figure. The rotating shaft 8 of the rotor 4 is supported in the front bracket 12 and the rear bracket 13 by means of bearings 15, 16. A pulley 17 is secured to one end of the rotating shaft 8, and the revolutions of an engine (not shown) are transmitted to the pulley 17 by means of a belt (not shown), rotating the rotor 4.
A rectifier 18, which converts an alternating current resulting from an alternating voltage induced by the stator coil 3 to a direct current, and a voltage regulator 19, which regulates the terminal voltage of the vehicle alternator at a fixed value by measuring the generated voltage and controlling the magnetizing current, are disposed radially outwards from the slip rings 9. Brushes 21, which are held by brush holders 20, are pushed into contact with the slip rings 9.
Resin fans 33 with resin blades 33a formed integrally in one side thereof are disposed on end surfaces of the polar cores 5, 6. Details of the mounted construction of the resin fans 33 are shown in FIG. 13, which is a cross-section of a side elevation of a circumferential portion of a resin fan 33, and in FIG. 14, which is a front elevation of the circumferential portion of the resin fan 33.
An annular protrusion 33b is formed integrally on an inner circumferential edge of the resin fan 33. Apertures 33c for bolts are disposed radially outwards from the annular protrusion 33b so that the resin fan 33 can be mounted on the end surface of the polar core 5. An annular recess 5b is disposed in the end surface of the polar core 5, and the annular protrusion 33b of the resin fan 33 is inserted therein. Metal braces 34 composed of bent sheet metal are placed axially outwards on the inner circumferential edge of the resin fan 33, the metal braces 34 are secured to the resin fan 33 by bolts 35, and the resin fan 33 is mounted on the end surface of the polar core 5 by bolts 32.
In a vehicle alternator of this kind, when the rotor 4 is rotated, an alternating voltage is induced in the stator coil 3, power is supplied, and heat is generated. The ventilation resulting from the rotation of the resin fans 33 cools the stator 1 and the rotor 4.
On the front bracket 12 side, a cooling ventilation generated by the rotation of the resin fan 33 is taken in through the air intake openings 12a in the front bracket 12, cools the stator 1, and is expelled through the air discharge openings 12b. On the rear bracket side, the cooling ventilation is taken in through the air intake openings 13a in the front bracket 13, cools the rectifier 18, the voltage regulator 19, and the stator 1, and is expelled through the air discharge openings 13b. Resin fans 33 are used here because, compared to sheet metal fans, their shape can be modified easily to improve performance and reduce noise, and their parts are lighter.
However, resin fans suffer from the following problems:
because they are made of resin, welding such as electric resistance welding, etc., cannot be used to secure resin fans to the polar cores of the rotor as it can be with sheet metal fans, and the same welding equipment used to secure sheet metal fans therefore cannot be used on resin fans; PA1 braces and bolts are required, which increases the number of parts; and PA1 since the braces have to be fastened with bolts, productivity decreases. PA1 a rotor having polar cores which hold a magnetizing coil which is secured to a rotating shaft; and PA1 a resin fan disposed on an end surface of the polar core; PA1 wherein a metal plate is provided to allow the resin fan to be secured to the end surface of the polar cores by welding. PA1 an annular flange portion which damps the resin fan to the polar core; and PA1 a plurality of cylindrical portions disposed in a circle concentric to the flange portion. PA1 a flange portion which clamps the resin fan to the polar core; and PA1 a cylindrical portion. PA1 an annular flange portion which clamps the resin fan to the polar core; PA1 a hollow cylindrical portion having one edge connected perpendicularly to the inner circumferential edge of said flange portion; and PA1 a flat annular plate portion connected to the other edge of the hollow cylindrical portion, which extends radially inwards from the hollow cylindrical portion. PA1 a rotor having polar cores which hold a magnetizing coil which is secured to a rotating shaft; and PA1 a resin fan disposed on an end surface of the polar core; PA1 the method of manufacture comprises the steps of: PA1 securing a metal plate to the resin fan by insertion molding; and PA1 securing the metal plate to the polar core by welding. PA1 a rotor having polar cores which hold a magnetizing coil which is secured to a rotating shaft; and PA1 a resin fan disposed on an end surface of the polar core; PA1 the method of manufacture comprises the steps of: